Add additional user info to the confirmation email

-- HikaShop version -- : 2.5.0
-- Joomla version -- : 3.4.3
-- PHP version -- : 5.5.23
-- Browser(s) name and version -- : firefox 38.0.5

I'm trying to add the username to the Order status notification email. Specifically to the BILLING_ADDRESS block.

I've tried editing the Order status notification with the following but it doesn't display the isername

<!--{IF:BILLING_ADDRESS}--><td><p>{VAR:BILLING_ADDRESS}</p>
<p>{VAR:username}</p></td><!--{ENDIF:BILLING_ADDRESS}-->

And to the address_template like following with no luck as well

defined('_JEXEC') or die('Restricted access');
?>{address_title} {address_firstname} {address_lastname}
<?php echo JText::sprintf('TELEPHONE_IN_ADDRESS','{address_telephone}');?><br/>
<?php echo JText::sprintf('HIKA_USERNAME','{username}');?><br/>

can anyone help with this?